Guns seized by the New York Police Department are displayed during a press conference on August 19, 2013. / Andrew Burton Getty Images

by John Bacon, USA TODAY

by John Bacon, USA TODAY

An undercover operation in New York has resulted in the largest seizure of illegal firearms in city history -- and has provided more ammunition in the city's defense of its controversial stop-and-frisk policy, Mayor Michael Bloomberg said Monday.

Police seized 254 illegal guns and indicted 19 people, Bloomberg said. The weapons included high-capacity assault weapons, a fully automatic machine gun and handguns, "which are most typically the models of guns used to commit violent crimes" in the city, Bloomberg said.

Two major defendants, operating independently, made numerous trips over the last year between their home states and New York City, personally transporting as many as 14 illegal firearms at a time using economy bus lines operating in the vicinity of Manhattan's Chinatown, police said in a statement.

Sales generally took place within hours of Walter Walker, 29, of Sanford, N.C., and Earl Campbell, 24, of Rock Hill, S.C., arriving in New York with a load of guns, police said.

Sixteen arrests were made in New York City, North Carolina and South Carolina in a series of apprehensions that began Aug. 2, the mayor's office said. The other three suspects were already in custody on unrelated charges.

Bloomberg said court-authorized wiretaps helped investigators identifiy the gun sellers in North and South Carolina attempting to supply guns for the purpose of reselling the weapons in New York City.

Bloomberg also provided a transcript of a comment attributed to suspect Campbell in a wiretap that indicated the city's controversial "stop and frisk" policy made selling weapons in the city more difficult: "I can't leave until you come, cause I can't take them (guns) to my house, to my side of town cause I'm in Brownsville (a section of Brooklyn). So we got like, whatchamacallit, stop and frisk."

Last week a federal judge ruled that the city's policy was unconstitutional because it disproportionately targets blacks and Hispanics. The city is appealing Judge Shira Scheindlin's decision, arguing the policy targets high-crime neighborhoods and rejecting Scheindlin's finding that the policy is a form of "indirect racial profiling."

More than half of the weapons seized were funneled to the city from North Carolina, with the remainder brought into New York City from South Carolina, Bloomberg said. Both states have relatively weak laws that allow criminals and traffickers to easily obtain guns, he said.

One of the discount bus companies charges $60 one-way from Raleigh, N.C., to New York. The fare is about half that charged by Greyhound, which, unlike the Chinatown buses, requires identification for boarding.

Walker met two times last year with the middleman and the undercover officer at a Brooklyn recording studio to sell the undercover firearms, the indictment said. He also allegedly sold weapons to the undercover officer in April in Manhattan.

In January, the undercover met with Campbell and his girlfriend, who was carrying assault rifle parts in her zebra-striped suitcase, authorities said. The girlfriend tried to assemble the weapon using an instructional video she called up on her smartphone. When she failed, the undercover bought the pieces anyway for $1,100.

One defendant, Jeremiah Devon McDougald, is accused of robbing someone at gunpoint while on the run from authorities in North Carolina, triggering an extensive manhunt. He was arrested on Aug. 7 and faces additional charges in North Carolina in connection with the robbery, police said.

Another defendant who became a fugitive, Chris Hill, evaded arrest for nearly two weeks before he was arrested Aug. 14 in Sanford, N.C. Police said Hill had a gun when he was arrested, and now faces additional charges as a felon in possession of a firearm in North Carolina.